threads: add initialization callbacks

For library users and plugins that need to hook into the thread life
cycle, perhaps to initialize some thread storage.

src/Makefile.am

@@ -438,6 +438,7 @@ noinst_HEADERS = \
 	suricata-common.h \
 	suricata.h \
 	suricata-plugin.h \
+	thread-callbacks.h \
 	thread-storage.h \
 	threads-debug.h \
 	threads.h \
@@ -991,6 +992,7 @@ libsuricata_c_a_SOURCES = \
 	stream-tcp-sack.c \
 	stream-tcp-util.c \
 	suricata.c \
+	thread-callbacks.c \
 	thread-storage.c \
 	threads.c \
 	tm-modules.c \

src/thread-callbacks.c

@@ -0,0 +1,55 @@
+/* Copyright (C) 2024 Open Information Security Foundation
+ *
+ * You can copy, redistribute or modify this Program under the terms of
+ * the GNU General Public License version 2 as published by the Free
+ * Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2 along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#include "thread-callbacks.h"
+
+typedef struct ThreadInitCallback_ {
+    SCThreadInitCallbackFn Callback;
+    void *user;
+    struct ThreadInitCallback_ *next;
+} ThreadInitCallback;
+
+static ThreadInitCallback *init_callbacks = NULL;
+
+bool SCThreadRegisterInitCallback(SCThreadInitCallbackFn fn, void *user)
+{
+    ThreadInitCallback *cb = SCCalloc(1, sizeof(*cb));
+    if (cb == NULL) {
+        return false;
+    }
+    cb->Callback = fn;
+    cb->user = user;
+    if (init_callbacks == NULL) {
+        init_callbacks = cb;
+    } else {
+        ThreadInitCallback *current = init_callbacks;
+        while (current->next != NULL) {
+            current = current->next;
+        }
+        current->next = cb;
+    }
+    return true;
+}
+
+void SCThreadRunInitCallbacks(ThreadVars *tv)
+{
+    ThreadInitCallback *cb = init_callbacks;
+    while (cb != NULL) {
+        cb->Callback(tv, cb->user);
+        cb = cb->next;
+    }
+}

src/thread-callbacks.h

@@ -0,0 +1,54 @@
+/* Copyright (C) 2024 Open Information Security Foundation
+ *
+ * You can copy, redistribute or modify this Program under the terms of
+ * the GNU General Public License version 2 as published by the Free
+ * Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2 along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#ifndef SURICATA_THREAD_CALLBACKS_H
+#define SURICATA_THREAD_CALLBACKS_H
+
+#include "suricata-common.h"
+#include "threadvars.h"
+
+/** \brief Function type for thread intialization callbacks.
+ *
+ * Once registered by SCThreadRegisterInitCallback, this function will
+ * be called for every thread being initialized during Suricata
+ * startup.
+ *
+ * \param tv The ThreadVars struct that has just been initialized.
+ * \param user The user data provided when registering the callback.
+ */
+typedef void (*SCThreadInitCallbackFn)(ThreadVars *tv, void *user);
+
+/** \brief Register a thread init callback.
+ *
+ * Register a user provided function to be called every time a thread is
+ * initialized for use.
+ *
+ * \param fn Pointer to function to be called
+ * \param user Additional user data to be passed to callback
+ *
+ * \returns true if callback was registered, otherwise false if the
+ *     callback could not be registered due to memory allocation error.
+ */
+bool SCThreadRegisterInitCallback(SCThreadInitCallbackFn fn, void *user);
+
+/** \internal
+ *
+ * Run all registered flow init callbacks.
+ */
+void SCThreadRunInitCallbacks(ThreadVars *tv);
+
+#endif /* SURICATA_THREAD_CALLBACKS_H */

src/tm-threads.c

@@ -29,6 +29,7 @@
 #include "suricata.h"
 #include "stream.h"
 #include "runmodes.h"
+#include "thread-callbacks.h"
 #include "threadvars.h"
 #include "thread-storage.h"
 #include "tm-queues.h"
@@ -1012,6 +1013,8 @@ ThreadVars *TmThreadCreate(const char *name, const char *inq_name, const char *i
     if (mucond != 0)
         TmThreadInitMC(tv);
 
+    SCThreadRunInitCallbacks(tv);
+
     return tv;
 
 error: